Dressing attachment



A w. ERDMAN mwssme ATTACHMENT Sept. 15, 1925.

Filed Aug. 24

INVENTQR flzchnm z BY 7! ,6 We% I ATTORNEY Patented Sept. 15, 1925.

UNITED STATES 1,553,524 PATENT OFFICE.

ALBERT W. ERDMAN, OF HARTFORD, CONNECTICUT, ASSIGNOR TO PRATT & WHITNEY COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

nnnssme ATTAQHMENT.

Application flied August 24, 1922. Serial No. 584,047.

To all whom it may concern:

Be it known that I, ALBERT W. ERDMAN, a citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented ,certain new and useful Improvements in Dressing -Attachments, of which the following is a specification.

My invention relates to dress1ng attachments for grinding wheels and particularly to dressing attachments for grinding wheels adapted to grind screw threads.

One object of my invention is to provide a dressing attachment for a grinding-wheel that shall be provided with means for dressing certain surfaces of the wheel to a cons vex form, whereby the wheel may be used to grind a screw thread without causing side interference which distorts the flanks of the thread.

Another object of my invention is to provide a dressing attachment for a grinding wheel that shall be provided with means comprising pins projecting from an ad ustable plate for engaging a curved surface on a dressing bar carrying a dressing tool to dress certain surfaces of the wheel to convex form, whereby the wheel may be used to grind a screw thread without causing side interference which distorts the flanks of the thread.

A further object of my invention is to provide a dressing attachment of the above indicated character that shall comprise a pivotally mounted body portion adapted to be swung into operative relation to a grind- 1 ing wheel, an adjustable plate mounted on the body portion and two bars carrying dressing tools and adapted to engage pins projecting from the adjustable plate, one of said bars having a curved surface for engaging said pins whereby certain surfaces on the wheel are trued to a convex form, the other bar having a straight surface for engaging said pins whereby one surface of the tool is dressed to a straight line contour.

In grinding screw threads, trouble is sometimes experienced by reason of side ,interference or the so-called side swiping by the grinding wheel. Such side interference by the grinding wheel is ractically negligible in threads having a sma 1 lead but increases with the lead of the thread. Each flank of a screw thread is generall formed by a cutting edge which is dispos radially with respect to the blank being operated on. However, in attempting to set agrinding wheel for; operation along a radial line, it is apparent the wheel will cut away a portion of the top and the bottom of the thread flank in accordance with the lead of the thread.

In thegrinding wheel customarily used for grinding screw threads, the V-shaped, or

double bevelled, periphery which engages the flanks of the thread is composed of surfaces having straight line contours. However, as above set forth, a grinding wheel comprising straigth line grinding surfaces will distort the shape of the screw thread being ground. The top and the bottom of the thread flank will be cut away.- If the U. S. standard thread is being ground, it is to be understood the periphery of the wheel is cut away in accordance with the shape of such thread.

A grinding wheel shaped by an attachment constructed in accordance with my invention is corrected to compensate for the side interference by the wheel. The sides of the V-shaped periphery of the grinding wheel are formed in the shape of convex surfaces whereby the cutting away of the top and the bottom parts of the screw flanks during the grinding operation is prevented.

In the grinding attachment constructed in accordance with my invention, a suitable body portion is pivotally mounted on a head of a grinding wheel. The body portion has a guideway formed in it for supporting an adjustable plate, suitable means being provided for adjusting such plate with respect to the body portion. Two dressing bars are provided for truing not only the bevelled grinding surfaces of the wheel but also for truing the straight line peripheral grinding surface of the wheel. Each dressing bar carries a dressing tool which preferably is an adjust-ably mounted diamond. Three pins, triangularly arranged project from the adjustable plate and serve as the guiding means for the bars during the dressing of the grinding wheel. The dressing bar, which serves to dress the bevelled surfaces ofthe grinding wheel, is provided with a convex surface for engaging the pins whereby convex surfaces will be formed on the grinding wheel. The dressing bar, which shapes the peripheral face of the wheel, is

' in wheel.

ing two of the projecting pins whereby a surface having a straight line contour is formed on the grinding wheel. The radius of the curved surface formed on one of the dressing bars is of such value as to form a convex surface on each side of the grinding wheel that will compensate for the side swiping or side interference which is usually experienced when grinding screw threads.

In the accompanying drawings:

Figure 1 is a side elevation of a wheel head provided with a dressing attachment constructed in accordance with my invention..

Fig. 2 is a view of the dressing attachment looking in the direction of the arrow marked 2 in Fig. 1 of the drawings.

Fig. 3 is a front view of the dressing attaclnnent looking in the direction of the arrow marked 3 in Fig. 1 of the drawings.

F ig- 4 is a transverse sectional view taken along the line 44 of Fig, 3 of the drawings.

Figs. 5 and 6 are respectively side and end views of the dressing bar utilized for dressing the bevelled surfaces of the grindig. 7 is a side view of the utilized for dressing the straight peripheral surface of the grinding wheel.

Referring to the accompanying drawings, a tool head 5 is provided with a grinding wheel 6 which is mounted on a shaft 7. Preferably the wheel 6 is provided with a i protective casing 8 which'forms part of the wheel head 5. The casing 8 is provided with oppositely disposed projections or lugs 9 which form a pivotal support for the frame or body portion 10 of the grinding attachment.

The body-portion 10 of the grinding attachment comprises two arms 11 and 12 which are secured to the lugs 9 by means of pins 13. It is apparent in the above construction the dressing attachment may be swung on the pins 13 into and out of operative relation to the grinding wheel 6. In Fig. 1 of the drawings, the grinding attachment is shown in full lines in operative relation to the grinding wheel and a portion of the grinding attachment is shown by dot and dash lines in a position out of operative relation to the grinding wheel. The forward ends of the arms 11 and 12 are secured to a block 14 by suitable screws 15.

A guidcway 16 is formed in the block 14 within which is fitted an adjustable plate 17. A screw 18, which is attached to the block 14 by means of a nut 19, is provided for adjusting the plate 17 with respect to the body portion of the grinding attachment. The screw is supported on the plate 17 and is held against movement on such plate by means of a collar portion 20 which is disposed between the top of the plate 17 and a dressing bar clamping member 21. The clamping member is fastened to the top of the plate 17- A suitable knurled handle 22 is provided for operating the screw 18.

Three pins 23, 24 and 25 project from the surface of the plate 17 for a purpose to be hereinafter set forth. Moreover, wearing blocks 26 are mounted in the plate 17 for a purpose to be hereinafter set forth. When the attachment is in operative position, a projection 27 provided on the attachment is in engagement with a stud 28 on the wheel head 5. A knurled nut 29 fastened to the stud 28 firmly holds the attachment in operative position.

As shown in Fig. 2 of thedrawings, the grinding wheel 6 is provided with two side surfaces 30 and 31 for grinding the flanks of a screw thread and a peripheral surface 32 which has a straight line contour for grinding the bottom of a U. S. standard thread. The side surfaces 30 and 31 of the grinding wheel are trued to a convex form in order to prevent a side interference by the grinding wheel during the grinding operation, as hereinbefore set forth.

In Figs, 5 and 6 is shown a dressing bar 33 which is adapted to shape the side surfaces 30 and 31 of the wheel to a convex form. able truing tool as a diamond 34, which is mounted in a screw The screw 35 is held in any set position by means of a set screw 36. The side 37 of the dressing bar is curved, as shown in Fig. 5 of the drawings, in order to guide the dressing tool to form convex surfaces on the grinding wheel. The surface 37 is shown adapted to form a convex surface on the grinding wheel but it is to be understood that other surfaces may be formed on the dressing bar for forming similar surfaces on the grinding wheel.

The dressing bar 33 carries a suit-- Preferably, pins 38 are provided on the bar 33 which may be grasped by the operator to aid in passingthe tool across the faces of the grinding .wheel- The curved surface 37 is adapted to engage the pins 23 and 25 when the surface 30 of the grinding wheel is being trued and is adapted to engage the pins 23 and 24 when the sur face 31 of the grinding wheel is being trued. The pins 23 to 25, inclusive, are so positioned on the plate 17 as to form the surfaces 30 and 31 at the desired angle or inclination.

Referring to Fig. 7 of the drawings, a

dressing bar 40 is shown for truing the peripheral surface 32 of the grinding wheel. The bar 40 carries a diamond 41 which is mounted on a screw 42. The screw 42 is held in any adjusted position by means of a 1 set screw 43. The surface 44 of the bar 40, which engages the pins 25 and 24 when truing the surface 32, as indicated in Fig. 2 of the drawings, is straight and has a straight line contour. Suitable pins 45, similar to the pins 38 on the bar 33, are provided which may be grasped by the operator to aid in passing the tool across the face of the grind the w eel. Moreover, it will be noted that by varying one surface of one of the dressing .bars, the side or bevel surfaces of the grlnding wheel may be formed to any desired contour.

thread with a .invention and such modifications are intended to be covered by the appended claims.

What I claim is: 1. In a truing attachment for a screw thread grinding machine, the combination with a body portion, a plate mounted on the body portion, and means for adjusting said plate relative to the body portion, of guiding means on said plate, a dressing tool comprising a bar having a truing tool mounted thereon, said bar having a curved surface for engaging said guiding means to form curved surfaces on the sides of the wheel being dressed.

2. In a truing attachment for a screw thread grinding machine, the combination with a body portion, and a bar carrying a truing tool, of three pins carried by said body portion and engaging the side of said bar havin a predetermined contour for guiding the ar to form convex contours on each side of the wheel being dressed.

3. In a truing attachment for a screw inding machine, the combination ody portion, and a plate slidably mounted on the body portion, of a dressing toolcomprising a bar having a truing tool mounted thereon and three guide pins for guiding said bar to dress two side surfaces on the grinding wheel, said bar having a curved surface for engaging the ide pins to form curved surfaces on the w eel being dressed, and a second dressing tool for engaging two of said pinsto dress the periphery of the grinding wheel.

4.11; a truing attachment for a screw thread grinding machine, the combination comprising a body portion pivotally mounted whereby it may be swung into and out of operative position adjacent a grinding wheel, two dressing tools adapted to be mounted on'said body portion, and guiding means on said body portion comprising pins carried by the body portion for controlling one of said dressing tools to form a nonrectilinear contour on two side surfaces of the wheel and for guiding the other dressing tool to dress the periphery of the grinding wheel.

5. In a truing attachment for a screw thread grinding machine, the combination comprising a body portion pivotally mounted whereby it may be swung into and out of operative position adjacent a grinding wheel, a bar mounted on said body portion and carrying a truing tool, and three pins carried by said body portion for guiding the bar carrying the truing too-l, said bar having a non-rectilinear surface enga ing said pins for guiding the truing tool to orm a non-rectilinear contour on a plurality of surfaces on the wheel.

6. In a truing attachment fora screw thread grinding machine, the combination with a body portion having a guideway thereon, a plate supported on the body portion and movable in said guideway, and

three pins projecting from said plate, of

two bars carrying truing tools, one of said bars engaging the pins to form convex surfaces on the sides of a grinding wheel and the other bar engaging two of said pins to true the peripheral surface of a grinding wheel.

7 In a truing attachment for a screw thread grinding machine, the combination with a body portion having a guideway thereon, a plate supported on the body portion and movable in said guideway, and three pins projecting from said plate, of a.

bar carrying a truing tool and having a curved surface for engaging said gins, said pins cooperating with said curve surface for guiding the truing tool to form a con vex surface on each side of a grinding wheel, a second bar carrying a truning tool, said second bar being guided by twoof said pins for truin the peripheral surface of a grind ing wheel.

In testimony whereof, I hereto afiix my signature.

ALBERT W.'ERDMAN. 

